1. Field of the Invention
The present invention relates to an engraving plastic sheet which is to be engraved by a suitable engraving means to present desired patterns or images and which is difficult to tamper, and hence, is suitable for use as a material of, for example, various types of cards, passport and bankbook.
2. Description of Related Art
Engraved plastic sheets having various patterns engraved therein have been known and used as, for example, ID cards which enable identification of individual persons. In recent years, passports made of such engraved sheets are used. Checking of examination of such engraved sheets are done by means of light reflected from the sheet and, hence, it is not easy to find any tamper of the sheets. Various types of sheets have been proposed to obviate this drawback but all these proposed sheets are still unsatisfactory.